Drug dependence is a serious public health problem. The acquisition of drug self-administration behavior is sensitive to the effects of stress. Certain stressors such as abuse and neglect can lead to long-term, even lifelong, increases in risk for drug self administration. The molecular mechanisms underlying these very long- term changes in vulnerability are not known. Of all known molecular mechanisms, methylation of CpG dinucleotides in the promoter region of genes is the longest lasting, and leads to very durable repression of gene expression. The work described in this application is directed at exploring the possibility that changes in CpG methylation in the promoter elements of genes in pathways critical for drug-related behavior mediate these long term behavioral changes. Neonatal mice will be randomized to maternal isolation or no treatment, and adolescent and adult mice will be randomized to chronic corticosterone, foot-shock stress, or no treatment. Animals will then be tested at a fixed age as adults on a cocaine self-administration paradigm. RNA and genomic DNA will be collected from a variety of brain regions with suspected roles in drug related behavior. A candidate gene approach as well as a whole-genome approach will be used to explore alterations in promoter methylation, and changes will be related to cocaine self-administration behavior in individual mice. This work will provide the foundation for future studies directed at understanding the molecular basis for stress effects on the acquisition of drug self administration. Drug dependence is a serious public health problem. Individuals with a history of abuse or neglect are at increased risk for trying drugs and becoming dependent on them, even well after the stress has subsided. This work examines the role of a specific molecular mechanism known as DNA methylation in these long- term changes in risk. [unreadable] [unreadable] [unreadable]